Solid Queue is a DB-based queuing backend for Active Job, designed with
simplicity and performance in mind.

Besides regular job enqueuing and processing, Solid Queue supports delayed jobs,
concurrency controls, recurring jobs, pausing queues, numeric priorities per
job, priorities by queue order, and bulk enqueuing (enqueue_all for Active Job's
perform_all_later).

Solid Queue can be used with SQL databases such as MySQL, PostgreSQL or SQLite,
and it leverages the FOR UPDATE SKIP LOCKED clause, if available, to avoid
blocking and waiting on locks when polling jobs. It relies on Active Job for
retries, discarding, error handling, serialization, or delays, and it's
compatible with Ruby on Rails's multi-threading.